pH meters generally have 5 solutions:
4.0, 7.0, and 10.0 solutions are used for calibration. Only use the 2 within the pH you are testing 4 though so 7.0 and 10.0.
Then there is a separate buffer for storage which is usually between 7.0-8.0. The 7.0 calibration buffer is your best bet to use. The electrode at the bottom needs to fully wet at all times so never dry it off. Use a container with a cap and cut a hole in the cap so that the probe can slide through the hole and fill the container with 7.0. There should also be fluid inside the probe at all times, which is a special buffer.
pH meters need to be calibrated every time they are used. If your electrode has dried, chuck it and get a new one. Even the probes that are mounted inside the tank need to be calibrated on a regular basis. And no, the pH should not fluctuate wildly while taking readings. It should steadily move. Make sure your not holding it by a powerhead or water outlet of some sort, but even that shouldn't make it go crazy. If not sure of the one you have but calibration should take about a min or 2, not hours. It sounds like yours has went bad, I would get a new one.
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